• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.287-293
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• 2004

A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, an 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two $D_2$injector pressure cases; 192 torr and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the $D_2$injection pressure is lower. But, the higher $D_2$injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of $D_2$injector increases, the maximum small signal gain in the $V_{1-0}$ transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.r.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.292-297
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• 2003

A diode-pumped single-mode Nd:YV $O_4$ green laser was developed. Frequency doubling of the laser was achieved by using an intracavity KTP generated green beam (532 nm). By comparing the diode laser spectrum with absorption spectrum of the Nd:YV $O_4$ crystal, we found optimal operating temperature of the diode laser. From output power measured for various mirror curvatures and cavity lengths, we found the optimal matching of TE $M_{00}$ mode with the pump beam gives the best efficiency. When the pump power was 1.9 W, 80 ㎽ of TE $M_{00}$ mode green beam was obtained. We tried to get a single longitudinal mode lasing as the fluctuation of the laser power was caused by the shift of longitudinal modes and the beating between the modes. We tested the intracavity etalon method and birefringent filter method for single mode operation. The etalon method resulted in the best single mode output power of 60 ㎽. The power fluctuation of the single-mode laser was reduced to 1/10 of that of the multi-mode laser.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.47-49
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• 1995

We report the spectroscopic properties of column-III nitrifies of GaN, GaInN, and AlGaN. The column-III nitride semiconductors are promising materials to realize the current-injection-type blue-and ultraviolet (UV)-light-emitting devices with high performance. To acheive the lasing with low threshold, the devices are must constructed to double heterostructure by succesive epitaxial growth technique, and we must confine the carriers in the potential barrier and optical confinement in wave guide between barrier and active layers has different refractive index. The refractive index of column-III nitride semiconductors, however, are rarely reported. The measured refractive index was 2.9, and the observed characteristic peak near the enrgy gap was analysed using a dielectric function and may due to excitonic contribution.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.153-158
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• 2009

Stable and tunable dual-wavelength erbium-doped fiber ring laser(EDFL) using a single fiber Bragg grating(FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 nm of wavelength under the electrical power with a 1000 mW. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.62-63
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• 2002

파장가변 색소 레이저 발진기는 반사형 회절격자에 비스듬히 입사하는 Grazing Incidence형 공진기 구조로 설계되었다.[1-2] 색소용액이 고속으로 순환되는 색소 셀에 여기광인 레이저 광원을 입사시키는 방법은 색소 셀과 색소 용액 순환방향 및 펌핑 광의 방향이 서로 수직을 이루도록 구성되어 있다. 또한, 두 개의 펌핑 광을 양방향에서 동시에 입사시킬 수 있도록 함으로써, 색소 셀 내부의 색소 용액이 여기 광을 균일하게 흡수하도록 설계하였다. (중략)

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.73-78
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• 2002

We have investigated the lasing characteristics of intracavity second harmonics of a Nd:YAG laser pumped by a laser diode. Through the analysis of the scalings of laminar phases, we verify that the second harmonics are generated through on-off intermittency. The intermittent behavior can be reproduced by a numerical simulation with rate equations.

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.339-346
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• 1993

Inproving laser efficiency, optimum content of Nd3+ which is active ion and effect of Cr3+ as a sensitizer are investigated in 60SiO2.30Li2O.10CaO host glass. The glasses are fabricated with the addition of Nd3+, Cr3+ and then optical properties such as absorption spectrum, fluorescence spectrum and fluorescence lifetime were studied. Finally, lasing efficiency was measured. From this study, optimum content of Nd2O3 appeared to be 3.5wt% and it was observed that the energy absorbed by optical exicitation of the Cr3+ is transfered to the Nd3+. Addition of Cr2O3 tend to improve characteristic of laser oscillation for the laser glass.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1045-1057
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• 2009

The authors investigated the InGaN/GaN multi-quantum well blue light emitting devices with the implementation of the photonic crystals fabricated at the top surface of p-GaN layer and the bottom interface of n-GaN layer. The top photonic crystals result in the lattice-dependent photoluminescence spectra at the wavelength of 450 nm and however, the bottom photonic crystal shows a big shift of the photoluminescence peak from 444 nm to 394 nm. The sample with the bottom photonic crystal structure also shows the lasing effect at the wavelength of 468 nm. Furthermore, the quality enhancement for the crystal growth of GaN thin film on the bottom photonic crystal comes from the modulated compressive stress which was measured by the micro-Raman spectroscopy.

• Journal of the Korean Institute of Navigation
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• v.16 no.2
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• pp.21-27
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• 1992

Shortening the lasing wavelength(particularly below infrared ; the visible region) of laser diodes is very attractive because it can provide a wide range of applications in the fields of optical information, measurement, sensor, the development of medical instrument, and optical communication through plastic fibers. According to the recent researches on the field, InGaAsP/GaAs was suggested as a material for red-light laser. In this study, in order to grow InGaAsP/GaAs epitaxial layer on InGaAsP/GaAs by LPE, we used GaP and InP two phase solution technique for 670nm and 780 nm region, respectively. Through the X-ray diffraction measurement for the epitaxial layer grown from the experiments, we found that the lattice mismatch of $In_{0.46}Ga_{0.54}As_{0.07}P_{0.93}$/GaAs and $In_{0.19}Ga_{0.81}As_{0.62}P_{0.38}$/GaAs was about +0.3% and +0.1%, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.7 s.337
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• pp.13-20
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• 2005

We propose an erbium-doped fiber ring laser whose multi-wavelength oscillation is tunable and switchable by tuning fiber bragg gratings. By applying axial pressure on the fiber bragg grating, the wavelength spacing of the proposed laser can be tuned continuously. And by adjusting a polarization controller(PC), the proposed laser can be switched among dual-, triple- and four-wavelength lasing operations.